It was as long ago as 1989 when I was responsible for the electrical services design of my first Data Centre. I was the Electrical Associate for Aukett, an architectural and building services consultancy based in Chelsea when we were appointed by Sun Alliance Insurance to design their new Data Centre in Southwater, Surrey. Sun Alliance were very keen to have total flexibilty and to avoid having any AC/Electrical plant within the machine hall (other than dual supply PDU's) which dictated the need to have an undecroft feeding the machine hall above and housing plant for a total electrical design load of 800kw including: Distribution switchgear N+1 (2no) 400hz frequency converters feeding IBM main frame computers N+1 (3no) 50hz 500kva rotary UPS Machine Hall mechanical plant including Chilled Water Units Halon bottles The remaining electrical plant was housed in an adjacnet plantroom housing: 2no 1000kva transformers substation N+1 (3no) 1250kva Standby deisel generators Main intake switchgear Lead acid batteries Mecanical plant MCC's etc So how would the design differ given the same brief today? Certainly there would not be the need for the 400hz frequency converters for main frame computers and the halon system would have to give way to halocarbon-based agents but the general layout would still provide a good solution. However the need for future capacity at the time was under estimated. The electrical design load of 800kw was meant to cater for 5years growth but less than a year later we were being appointed to build a new power house to double the capacity with the need to consider replacing the UPS/Batteries/Generators with Diesel Rotary UPS.